There is an increasing demand to perform real-time detection of hidden explosive devices such as explosives concealed in luggage, land mines, unexploded ordinance, and the like. This is an ever-growing problem due to the extreme low cost of explosive devices and the ease with which they can be deployed. For one example, security concerns at sensitive locations such as airports require that baggage and freight as well as personal effects be carefully screened for explosive devices. Such devices may be small and innocuous, and may not be readily detectable by other more conventional means such as visual inspection, x-ray or magnetic detection techniques. For a second example, anti-personnel land mines are relatively small devices generally constructed from plastic and other non-metallic materials. more than 110 million active mines are scattered in 64 countries. Also more mines are in stockpiles in countries all over the world. Many countries are infested with land mines. At the current rate, for every mine removed 20 more are laid. Every month over 2,000 people are killed or maimed by mine explosions. Old mine fields remain active, endangering non-combatants long after the war where they were used is over. On average, locating a single land mine is 100 times more expensive than the cost of the mine. It is estimated that at the current rate of removal, it will take a few thousand years to remove the land mines that already infest many countries. In addition to the humanitarian need for eliminating old mines, methods and apparatus for readily detecting and de-fusing land mines are needed by the Department of Defense.
Because many land mines are made of non-metallic substances, it is desirable to locate them using chemical techniques. Since the vapor pressures of many explosive substances are very low, a chemical detection technique with sensitivity of parts per trillion to parts per quadrillion is needed. Such high sensitivity now is achievable only with techniques such as mass spectroscopy or nuclear magnetic resonance, which require large and complex equipment. None of the technology currently available offers an extremely sensitive, hand-held, battery-operated explosive detector. An explosive detector that can give no false reading and can pinpoint explosive devices such as explosives concealed in luggage, unexploded ordinance and land mines with high efficiency is much needed in both military and civilian applications.